linux-kernel - Re: [PATCH v5 11/16] drm/vkms: Add YUV support

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Message-ID: <5f6ab3804baa87f6e2299f668d2ab41be3a13f13.camel@pengutronix.de>
Date: Wed, 27 Mar 2024 13:11:53 +0100
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Louis Chauvet <louis.chauvet@...tlin.com>, Rodrigo Siqueira
 <rodrigosiqueiramelo@...il.com>, Melissa Wen <melissa.srw@...il.com>, 
 Maíra Canal <mairacanal@...eup.net>, Haneen Mohammed
 <hamohammed.sa@...il.com>, Daniel Vetter <daniel@...ll.ch>, Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, arthurgrillo@...eup.net, Jonathan Corbet
 <corbet@....net>,  pekka.paalanen@...oniitty.fi
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	jeremie.dautheribes@...tlin.com, miquel.raynal@...tlin.com, 
	thomas.petazzoni@...tlin.com, seanpaul@...gle.com, marcheu@...gle.com, 
	nicolejadeyee@...gle.com
Subject: Re: [PATCH v5 11/16] drm/vkms: Add YUV support

Hi Louis,

On Mi, 2024-03-13 at 18:45 +0100, Louis Chauvet wrote:
> From: Arthur Grillo <arthurgrillo@...eup.net>
> 
> Add support to the YUV formats bellow:
> 
> - NV12/NV16/NV24
> - NV21/NV61/NV42
> - YUV420/YUV422/YUV444
> - YVU420/YVU422/YVU444
> 
> The conversion from yuv to rgb is done with fixed-point arithmetic, using
> 32.32 floats and the drm_fixed helpers.

s/floats/fixed-point numbers/

Nothing floating here, the point is fixed.

[...]
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index 23e1d247468d..f3116084de5a 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -99,6 +99,27 @@ typedef void (*pixel_read_line_t)(const struct vkms_plane_state *plane, int x_st
>  				  int y_start, enum pixel_read_direction direction, int count,
>  				  struct pixel_argb_u16 out_pixel[]);
>  
> +/**
> + * CONVERSION_MATRIX_FLOAT_DEPTH - Number of digits after the point for conversion matrix values

s/CONVERSION_MATRIX_FLOAT_DEPTH/CONVERSION_MATRIX_FRACTIONAL_BITS/

Just a suggestion, maybe there are better terms, but using "FLOAT" here
is confusing.

> + */
> +#define CONVERSION_MATRIX_FLOAT_DEPTH 32
> +
> +/**
> + * struct conversion_matrix - Matrix to use for a specific encoding and range
> + *
> + * @matrix: Conversion matrix from yuv to rgb. The matrix is stored in a row-major manner and is
> + * used to compute rgb values from yuv values:
> + *     [[r],[g],[b]] = @matrix * [[y],[u],[v]]
> + *   OR for yvu formats:
> + *     [[r],[g],[b]] = @matrix * [[y],[v],[u]]
> + *  The values of the matrix are fixed floats, 32.CONVERSION_MATRIX_FLOAT_DEPTH

s/fixed floats/fixed-point numbers/

regards
Philipp